Developments in semiconductor technology have created the capability to produce low-cost, highly reliable switches that are, effectively, implementations of mechanical relays. They have been found to be of particular use, when implemented, as single pole, single throw, type relays, but are not limited thereto. Semiconductor switches are being used more and more as replacements for the prior mechanical relays, due to the high switching speed available as well as their ability to transfer relatively high currents without failure. These switches are often referred to as transfer gates or pass transistors as they employ the characteristics of transistors—usually MOS transistors—to either permit or prevent the passage of a signal.
Switches are widely used in many fields including large- and small-scale consumer products, such as, but not limited to, automobiles, home electronics and personal electronics (e.g. cell phones, personal digital assistants and personal media players, etc.). They can be used as analog routers, gates, or relays, or as digital multiplexers, routers, or gates.